title: Optimization of fermentation conditions for the biosynthesis of L-threonine by Escherichia coli.
abstract: In this study, the fed-batch fermentation technique was applied to improve the yield of L-threonine produced by Escherichia coli TRFC. Various fermentation substrates and conditions were investigated to identify the optimal carbon source, its concentration and C/N ratio in the production of L-threonine. Sucrose was found to be the optimal initial carbon source and its optimal concentration was determined to be 70 g/L based on the results of fermentations conducted in a 5-L jar fermentor using a series of fed-batch cultures of E. coli TRFC. The effects of glucose concentration and three different feeding methods on the production of L-threonine were also investigated in this work. Our results showed that the production of L-threonine by E. coli was enhanced when glucose concentration varied between 5 and 20 g/L with DO-control pulse fed-batch method. Furthermore, the C/N ratio was a more predominant factor than nitrogen concentration for L-threonine overproduction and the optimal ratio of ammonium sulfate to sucrose (g/g) was 30. Under the optimal conditions, a final L-threonine concentration of 118 g/L was achieved after 38 h with the productivity of 3.1 g/L/h (46% conversion ratio from glucose to threonine).
authors.affiliation: College of Biotechnology, Tianjin University of Science & Technology, Tianjin 300457, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Chen
authors.forename: Jin
authors.initials: J
authors.lastname: Huang
authors.forename: Zhi-bin
authors.initials: ZB
authors.lastname: Feng
authors.forename: Lei
authors.initials: L
authors.lastname: Yu
authors.forename: Qing-yang
authors.initials: QY
authors.lastname: Xu
authors.forename: Ting-yi
authors.initials: TY
authors.lastname: Wen
mesh_terms: D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D004926:Escherichia coli / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D013912:Threonine / Q000096:biosynthesis*; D013997:Time Factors
chemical_list: D003470:Culture Media; D013912:Threonine; D002244:Carbon; D005947:Glucose